During their life cycle, plants may be at risk for exposure to environmentally stressful conditions. These conditions can include exposure to low temperatures and limited access to water (such as drought). If the duration or severity of these stressful conditions is too great, the exposed plants may have reduced growth and yield. While plants have mechanisms to mitigate the effects of environmentally stressful conditions, continuous exposure may cause damage to the plants and can result in death of the plant. Reduced crop yield or death of crop plants due to environmentally stressful conditions is a major concern of plant growers.
Crop growers desire to plant their crops as early as possible so that they can obtain the highest available yield during the growing season. Crop growers with a large acreage to plant also want to begin planting as soon as possible. Early planting, however, is not without risks. One risk is that the crops will be exposed to cold temperatures that may cause the seedlings or plants to suffer damage or death. Cold temperatures cause millions of dollars of damage to crops each year. In some parts of the United States, cold temperatures can occur at any time during the growing season. Cold temperature damage is most common, however, in the spring when the plants are vulnerable.
Unfortunately, if cold temperature damage occurs to a grower's crops, the grower is then faced with a dilemma. Currently growers must either replant their fields immediately, or wait for several days to see if their plants recover and then decide if they should replant their fields. If the growers wait for several days to see if their plants recover and the damaged plants do not, then they have wasted valuable time before replanting and further reduced their potential yields. If the plants appear to recover and the growers do not replant, then the growers will be concerned about the negative impacts on yield for the rest of the growing season. If the growers replant their crops, then they are spending valuable resources on damage mitigation that could have been spent elsewhere.
Drought is a common abiotic stress that limits the productivity of all major crops. About 80% of the agricultural land in the United States experienced drought in 2012, impacting 70 to 75% of corn and soybean acreage (United States Department of Agriculture, Economic Research Service, 2012). According to the United Nations, drought intensity is increasing worldwide (United Nations News Center, 2012). Even seasonal mild or moderate drought in critical growth stages can reduce yields by 20 to 50% on rain-fed farms or those with limited irrigation. According to the National Climatic Data Center, both moderate and severe to extreme drought is becoming more common. Coupled with the increasing depletion of water resources, there is a need for new products and solutions to meet drought stress. Several approaches are being used with varying levels of success to address this problem including agronomics, traditional plant breeding, genetic engineering and chemical treatments. Each of these strategies has potential benefits, but also significant shortcomings.
Chemicals that have been promoted and used commercially to alleviate the effects of drought in crop plants include abscisic acid, anti-transpirants, and triazole fungicides and growth inhibitors (e.g. tebuconazole). For example, anti-transpirants reduce gas exchange and thus inhibit water loss. However, reduction of gas exchange inhibits photosynthesis, and thus slows plant growth. Although these chemicals may be effective at combating drought, they may not be acceptable for use in field crops due to negative effects on yield, cost, adverse side effects, or short duration of effect.
Accordingly, there is a need for new methods for protecting crop plants from the stressors of low temperatures and drought. The new methods should be cost-effective for the growers and produce consistent and reliable protection.